Ship&#39;s propeller and impeller propeller



Oct. 26, 1954 s. SPARLING SHIP'S PROPELLER AND IMPELLER PROPELLER 6Sheefs-Sheet 1 Filed May 29, 1952 Sy/ves/e/ Spar/mg Y By his attorneysMMM Oct. 26, 1954 s. SPARLING 2,692,572

SHIPS PROPELLER AND IMPELLER PROPELLER Filed May 29, 1952 6 Sheets-Sheet2 hymen/or Sy/veszer Spar/mg By his al/omeys Oct. 26, 1954 s. SPARLING2,592,572

SHIP'S PROPELLEZR AND IMPELLER PROPELLER Filed May 29, 1952 6Sheets-Sheet 5 /nvenf0r Sy/vesfer Spar/mg By his at/omeys Oct. 26, 1954s. SPARLING SHIPS PROPELLER AND IMPELLER PROPELLER 6 Sheets-Sheet 4Filed May 29, 1952 By her 0/ fomeys Oct. 26, 1954 s. SPARLING SHIPSPROPELLER AND IMPELLER PROPELLER e Sheefs-Sheet 5 Filed May 29, 1952 //ne/7/0r S /vesfer5 ar/i ,fleceasea By /rene 5f gar/2 Execufnx Byheraffameys 06%. 26, 1954 s SPARLING 2,692,572

SHIP'S PROFELLER AND IMPELLER PROPELLER Filed May 29, 19,52 6 SheetSSheet 6 Sy/ves/erSparflng, Deceased By/rene B. Spar/mg, EXecu/r/x By herafforneys Patented Oct. 26, 1954 UNHT OFFICE SHIPS PROIPELLER ANDIIVEELLER PROPELLER Application May 29, 1952, Serial No. 290,696

17 Claims. 1

This application is a continuation-in-part of application Ser. No.178,383, filed August 9, 1950, in the name of Sylvester Sparling. Thatapplication has been abandoned.

The present invention relates to ship-propelling apparatus and moreparticularly to such apparatus wherein a primary screw or jet propeller,or other propelling device, operating in a known manner, activates animpeller which in turn drives a secondary propeller to impart additionalpropelling effort to the ship. The invention is especially useful in itsapplication to slowspeed ships, to which use, however, it is notrestricted.

The invention provides an impeller-propeller unit acting as auxiliarypropelling means wherein the entire lip stream from the primarypropeller or jet propulsion means is captured and effectively used by animpeller separately carried by the ship. Furthermore, air bubbles arekept out of the slip stream within the impeller so that the sli streamdelivers a heavy impact and thrust against the impeller blades. There isa secondary propeller, carried by the ship and outside the impeller.This secondary propeller turns with the rotating impeller and impartsadditional propelling eifort to the ship through the which mounts itindependently and directly on the ship. The independently carriedimpeller-propeller unit does not interfere with operation of the primarypropeller, and imposes no burden thereon.

In the accompanying drawings:

Fig. 1 is a semi-diagrammatic view, partly in section, of the stern of apropeller-driven ship with one embodiment of the novel propellingapparatus applied thereto, parts being broken away and the dot-and-dasharrows showing the directions of movement of the water.

Fig. 2 is a semi-diagrammatic view in end elevation illustrating theprimary propeller and the position of the shell of the impeller of theinvention with respect thereto; the view being taken forward of thepropeller looking aft on the line 2-2 of Fig. 1.

Fig. 3 is a view similar to Fig. 2 but showing only the impeller andprimary propeller blades of the embodiment of Figs. 1 and 2; the pointmarked with the arrow V being in Fig. 1 in down position.

Fig. i is a detail plan view of the hub of the impeller-propeller unitof the embodiment of Figs. 1-3.

Fig. 5 is a view similar to Fig. 1, of a preferred embodiment of theinvention in which there are twelve impeller blades.

Fig. 6 is a face view in elevation looking to the 2 rear, showing theimpeller-propeller arrangement of the embodiment of Fig. 5.

Fig. '7 is a developed detail view of part of the shell and blades ofthe unit of Figs. 5 and 6, showing a modified form.

Fig. 8 is a view similar to Fig. '7, of another form of shell andimpeller blades peculiarly adapted for backing the ship.

Fig. 9 is a View similar to Fig. 6, of an improved arrangement ofimpeller blades in which there are eighteen blades.

Fig. 10 is a view similar to Figs. 1 and 5 of one of the novelimpeller-propeller units installed on a ship driven by jet propulsion.

Fig. 11 is a view similar to part of Figs. 1 and 5 in which the mainpropeller shaft and the hub of the impeller-propeller unit areinterfitted to prevent lateral vibration, but turn freely with relationto each other.

In the embodiment of the invention illustrated in Figs. 1-4 of thedrawings there is shown the stern of a ship ill carrying the novelship-propelling apparatus which is the subject of the present invention.In the ship shown there is a primary propeller comprising three blades 1IA, l i3 and l lC fixed to a propeller shaft E2 of the ship ill in theusual manner. The shaft is driven by any desired prime mover 22. Behindthe primary propeller l l, and independently thereof, the ship carries aseparate novel impeller-propeller apparatus l3 for rotation coaxiallywith the primary propeller. The object of the separateimpeller-propeller apparatus is to capture and convert into additionalpropelling effort impulses from the slip stream of the primary propellerwhich ordinarily are wasted, and to do so with but little increase inthe load on the ships engine.

As here shown, the mounting of this secondary apparatus comprises astrut i l hanging from the overhang 15 of the stern of the ship I G.This strut carries a shaft 16 coaxial with but behind the propellershaft E2 of the ship. These two shafts are not connected to each other.The impeller-propeller apparatus 13 is rotatably carried by the shaft 56. Although the shaft may be fixed to the strut M and the separateimpeller-propeller apparatus is rotated thereon, it is preferred thatthe shaft be rotatably carried by the strut. Therefore, there is shown arotatable connection between the shaft and the strut in Fig. l, afore-and-aft thrust bearing ll serving to prevent axial movement of theshaft IS with respect to the strut, and also to transfer to the strutany force exerted upon the shaft I6.

impeller-propeller apparatus I3 is carried upon the shaft it by means ofan impeller hub 3 l8 coaxially fitted upon the shaft. In the drawings,merely for the sake of illustration, is shown the shaft IE rotatable inthe strut and the hub tight upon the shaft.

The impeller of the impeller-propeller apparatus l3 comprises blades l9centrally fixed to the hub I8 and extending outwardly therefrom ingenerally radial directions. Six such impeller blades 19A, 19B, 19C,19D, [9E and 19F are shown in Fig. 3 of the drawings. More blades may beused. A cylindrical casing, cylinder or shell 20 is carried by the outerends of the impeller blades coaxial with the impeller hub [8. In orderthat the impeller may receive substantially the entire slip stream ofthe primary propeller l i, the cylindrical shell 20 is disposed with itsforward end surrounding the rear part of the primary propeller (see Fig.1). Thus the back, i. e., rear or pumping edges of the primary propellerblades are inclosed by the cylindrical shell. The diameter of the shellis such that it closely surrounds the outermost edges of the primarypropeller (see Fig. 2). On the other hand, the axial extent of thecylindrical shell 20 is such that the forward or suction edges of theprimary propeller blades are in open water, and there is no interferencewith the effective operation of the primary propeller. The cylindricalshell accordingly receives and confines therein substantially the entireslip stream, and its axial extent rearwardly of the primary propellercauses the impeller blades to react fully to the energy of the slipstream. The primary propeller and the impeller-propeller apparatus [3both turn in the same direction as indicated by the long arrows in Figs.2 and 3. Looking aft, they turn counterclockwise.

The impeller blades I9 are carefully designed and arranged to turn theimpeller-propeller apparatus I3 with greatest efficiency. It is foundadvantageous to position the impeller blades as closely as possible tothe pumping edges and the outermost ends of the primary propellerblades. Accordingly, the forward edges of the impeller blades !9 areformed to follow the contour of the pumping edges of the primarypropeller blades, and are positioned as closely thereto as is consistentwith necessary operating clearance (see Fig. 1). Because of thisconstruction the slip stream from the primary propeller I I is preventedfrom moving ineffectively within the impeller.

Furthermore, the impeller blades [9 are formed and fixed in position toextend rearwardly of the impeller from their forward edges for abouttwo-thirds of their length in planes parallel to the axis of theimpeller hub H3. The rear onethird of each impeller blade is curved outof such substantially longitudinal direction, as indicated in Fig. 1. Inthis figure impeller blade HE is above horizontal leaning toward theobserver and blade 19C is 30 below horizontal. Propeller blade NC is 30below horizontal facing toward the observer. It has been found that theaction of the slip stream upon blades so formed and disposed gives moreefiective thrust upon the blades than is the case where flat bladeshaving more or less pitch are used.

With the impeller and its blades constructed and arranged as described,efficient action of the slip stream to rotate the impeller-propellerapparatus is assured. Substantially the entire slip stream is receivedwithin the impeller. The lateral thrust, or the radial and centrifugalcomponents of the slip stream, impinge upon the forward parts of theimpeller blades to give initial turning impulses thereto (see the pairsof dotand-dash arrows on blade 19B in Fig. l). The angle of impingementis about '70-80, as indicated by the pair of arrows. As the initialturning energy of the slip stream is converted into turning movement ofthe impeller-propeller apparatus, the water of the slip stream isdirected rearwardly by the impeller blades I!) (see the singledot-and-dash arrow on blade i913 and the dash arrow hidden by blade I9C)As this rearwardly moving water comes into contact with the curved rearone-third of the impeller blades, it gives a second turning impulse tothe impellerpropeller apparatus. Finally, a third thrust is given as therearwardly moving water of the slip stream is deflected off of the endsof the impeller blades and leaves the impeller.

In order that rotation of the impeller-propeller apparatus may impartthe additional propelling effort to the ship through the strut M, asecondary propeller is carried by the impeller externally thereof tocomplete the apparatus. Thus, as the impeller is rotated by the slipstream, the secondary propeller turns with the impeller and exerts athrust against the clear water outside of the impeller. The reaction ofthe water to this thrust is carried through the impeller and the shaft[6 to the strut M. Instead of employing a single continuous secondarypropeller blade, it is found convenient to provide separate secondarypropeller blades, and three such blades 2 IA, MB and 2 IC are shown inFigs. 1 and 3 of the drawings.

In order to eliminate loss of energy through air bubbles and to securethe most power from the water in the slip stream from the primarypropeller, means is provided for removing air bubbles from the slipstream within the impeller. For this purpose the forward end of theimpeller hub I8 is made of the same diameter as the after end of theprimary propeller hub, and it is positioned as closely adjacent theretoas possible. The diameter of the impeller hub 18 is increased rearwardlythereof to give the hub a cone formation (see Fig. 4). As a result offorming and positioning the impeller hub as described, the water passingthrough the impeller is compacted by the removal of air bubblestherefrom.

As a result of the invention, substantially the entire slip stream fromthe primary propeller is captured and its energy is effectively used bythe impeller. The impeller-propeller apparatus is carried entirelyseparate from the primary propeller. It applies the energy which itreceives from the slip steam to the ship separately from the mainpropeller and main propeller shaft. The impeller-propeller apparatusdoes not interfere with effective operation of the primary propeller;and no direct burden is imposed upon the primary propeller by theimpeller-propeller apparatus. But slight increase in power is requiredof the ships engine due to restriction of the slip stream by theimpeller. By practical test it is found that the present invention makesit possible for the primary propeller to attain of rated shaft horsepower. Adding thereto 40% from the slip stream gives a total of ratedshaft horse power.

In many cases it is desirable to extend the cylindrical shell forward tothe point where the shell ends opposite the forward or suction edges ofthe primary propeller. Such a shell 23 is shown in the preferredembodiment of Fig. 5. The increase in length shown is about 10% andstarts from the center line of the primary propeller blades.

In Fig. 6 is shown the use of twelve impeller blades 24 instead of six.It will be noted that the width of the blades is shown somewhat reduced.There are also shown six secondary propeller blades 25, each of which isshorter than the sec-- ondary propeller blades ZlA, B, C, of Fig. 3.

The number of impeller blades can be increased still further to, say,eighteen. In Fig. 9 is shown an embodiment in which there are eighteenimpeller blades. In this embodiment two kinds of blades are shown. Thereare six blades [9A, B, C, D, E, F, like those shown in Fig. 3.Intercalated between these are short intermediate blades 26. Theseinter-mediate blades are attached to the cylindrical shell 23 of theimpellerpropeller unit and extend radially inward half the distance tothe hub of the unit. Two such intermediate blades are shown between eachtwo regular blades. These intermediate blades are shown as half thewidth of the regular ones. This arrangement eases the passage of thewater through the impeller. In this embodiment three secondary propellerblades 35 are shown, as in the embodiment of Figs. 1-3.

It has been found that on many ships the operation of the primarypropeller pulls the water aft past the propeller faster than new watercan come in to replace it. As a result of this pumping action of theblades there is a partial vacuum immediately aft of the primarypropeller. In Figs. 5, 7 and 8 are shown means by which this vacuum ispartially neutralized. These means consist of vacuum relief ventsorholes 27 in the cylindrical shell of the impeller-propeller unit.These holes are located in a position immediately aft or immediatelyforward of the center of the primary blades, the hole preferably beinglonger circumferentially than it is lengthwise of the shell. In Fig. '7each hole is shown circumferentially as long as half the distancebetween the two propeller blades, assuming that there are six impellerblades in the impellerpropeller unit. The width of each hole is about /6of the length in the examples shown in the drawings.

Another feature of the invention relates to the shaping of the impellerblades. As will be realized from the description heretofore given, it isvery important in the present construction that both radial and axialcomponents of movement of the slip stream be dealt with. It has beenfound not only that the slip stream is composed of two elements ofenergy, one lateral and the other working straight aft (and advantage ofboth components has been taken in the present invention), but also thatthe shape of the impeller blades can be varied slightly to give greaterefficiency according to the kind of work for which the ship is built. InFig. 4 are shown impeller blades which are curved at the aft end, and ithas been found that this is the most efficient type of blade forlong-range or coastwise hauling where a vessel is moved to and from thedock by tugs rather than by its main propelling equipment. On the otherhand, in smaller vessels, such for example as harbor craft, whereconsiderable maneuverability has to be obtained from the main propellingequipment, it is found that the curved type of impeller blades is not asefficient when the engines are reversed as are the constructions shownin Figs. '7 and 8. In these figures the after ends of the blades arecomposed of either a single flat section 28, as

shown in Fig. 8, or a plurality of smaller successive fiat sections 29,as shown in Fig. 7. By thus having the after section of each bladecomposed of one or more sections of flat plate, increased efficiency,nearly equal to that obtained by the unbroken curve shown in Fig. 4, isobtained when the propeller is rotating in the reverse direction.

In Fig. 11 has been shown an embodiment in which there is a rearwardlyprojecting stub 36 on the rear end of the primary propeller shaft. Thisfits freely into a hole in the front end of the impeller hub IS. The twoparts turn freely with relation to each other and there is no drivingaction between them. The purpose of this free interfitting is to preventrelative lateral vibration of the parts.

It will be obvious that ships propelled by jet propulsion rather than bythe ordinary bladed propeller can also benefit greatly from the presentinvention, and in Fig. 10 the present invention is shown embodied in ajet-propelled ship. In this figure the after end of a jet motor 30 isshown at the left, with the arrows indicating the direction of movementof the fluid when the ship is going forward. Just aft of the rear end ofthe motor, closely adjacent thereto, is one of the novelimpeller-propeller units carried on a bracket 31 bolted on the sternoverhang 32 of the ship. The cylindrical shell 33 in the unit is shownas of the same diameter as the opening at the rear of the jet motor, andthere are impeller blades 34 and secondary blades 35 of the same generalnature as those previously described. It will be seen that the inventionis equally applicable to screw propellers, jet propellers and othersimilar propelling devices or equipment.

It is desired to claim not only ship-propelling equipment or apparatuswhich includes the novel impeller-propeller unit, but also the unit byitself, since it may be possible in many instances to build and sell thepropeller-impeller unit separately.

What is claimed is:

l. Ship-propelling apparatus comprising primary propelling means at therear of the ship and an impeller-propeller unit carried by the shipseparately from and behind the primary propelling means, said unitcomprising in combination a cylindrical shell coaxial with the primarymeans of a diameter such that it surrounds the outermost edges of theprimary propelling means and adapted to confine substantially the entireslip stream received from the primary means, impellers including bladeslocated inside the shell, and secondary propelling means carriedexternally thereof in water outside the slipstream; thereby impartingadditional propelling eiiort to the ship as the unit is rotated by theslip stream.

Ship-propelling apparatus according to claim 1 in which the impellerslie radially inside the shell in a direction longitudinal thereof butare curved away from the direction of rotation of the unit at their endsremote from the propeller, whereby the energy of both axial andlongitudinal components of force in the slip stream are translated intorotation of the secondary blades in water outside the slip stream.

3. Ship-propelling apparatus according to claim 1 in which the forwardedges of the impellel' blades are fixed at an angle of substantially 70to 89 to the direction of the slip stream.

4. Ship-propelling apparatus according to claim 1 in which some of theimpeller blades extend only part way from the shell to the center,thereby easing the passage of the water through the impeller.

5. Ship-propelling apparatus according to claim 1 in which the impellerblades lie radially inside the shell in a direction substantiallylongitudinal thereof so as to receive the rotary component of force fromthe slip stream at an angle which will cause rotation of the unit andthe rear ends of the impeller blades are curved out of suchsubstantially longitudinal direction tocatch the longitudinal componentsof force in the slip stream so as to also cause rotation of the unit,thereby imparting additional propelling effort to the ship through thesecondary propelling means in the water outside the slip stream.

6. In ship-propelling apparatus a propeller shaft, a primary propelleron the shaft, and a cylindrical impeller carried by the ship separatelyfrom and behind the primary propeller and shaft in coaxial relationtherewith of a diameter such that it surrounds the outermost edges ofthe primary propeller and adapted to receive substantially the entireslip stream from the primary propeller, in combination with a secondarypropeller carried by the impeller externally thereof in water outsidethe slip stream for imparting additional propelling effort to the shipas the impeller rotates.

'7. Ship-propelling apparatus comprising a propeller shaft and a primarypropeller on the shaft, in combination with an impeller-propeller unitcarried by the ship separately from and behind the primary propeller andcoaxial therewith of a diameter such that it surrounds the outermostedges of the primary propeller and said unit having a cylindrical shelladapted to confine substantially the entire slip stream received fromthe primary propeller and extending forward to the forward edge of theprimary blades, impellers inside the shell lying radially in a directionlongitudinal of the shell with their ends remote from the propellercurved out of such substantially longitudinal direction and adapted totake energy from both axial and longitudinal components of force in theslip stream, and sec ondary propelling means carried externally of theshell in water outside the slip stream, whereby additional propellingeffort is imparted to the ship as the unit is rotated by the slipstream.

8. Ship-propelling apparatus according to claim 1 in which there is ahub in the propellerimpeller unit to carry the shell, and in which theimpeller blades lie radially inside the shell in a directionlongitudinal thereof but curved at their ends remote from the propeller,whereby the energy of both axial and longitudinal components of force inthe slip stream are translated into rotation of the secondary blades inwater outside the slip stream; the diameter of the hub increasingrearwardly so as to give the hub a cone formation to remove air bubblesfrom the slip stream within the impeller.

9. Ship-propelling apparatus comprising a propeller shaft, a primarypropeller fixed to the propeller shaft, impeller-propeller apparatuscarried by the ship separately from, located for rotation behind andcoaxial with, the primary propeller shaft, said impeller-propellerapparatus comprising a hub, in combination with a cylindrical impellercarried by the hub and of such diameter and so disposed that its endnearest the primary propeller surrounds the rear part of the primarypropeller to receive therein substantially the entire slip stream fromth primary propeller, and blades fixed within and forming part of theimpeller for reacting under the force of the slip stream to rotate theimpeller; and secondary propeller blades carried by the impellerexternally thereof in water outside the slip stream for impartingadditional propelling effort to the ship as the impeller rotates; thediameter of the hub increasing rearwardly thereof to give the hub a coneformation to remove air bubbles from the slip stream within theimpeller.

10. Ship-propelling apparatus comprising a propeller shaft, and aprimary propeller fixed on the propeller shaft, an impeller-propellerapparatus carried by the ship separately from, located for rotationbehind and coaxial with, the primary propeller shaft, saidimpeller-propeller apparatus comprising a hub in combination with ahollow cylinder coaxially fixed to the hub and carried thereby and ofsuch diameter and so disposed that its end nearest the primary propellersurrounds the rear part of the ships primary propeller to receivetherein substantially the entire slip stream from the primary propeller,impeller blades fixed within the cylinder for reacting under the forceof the slip stream to rotate the blades and cylinder, and secondarypropeller blades carried by said cylinder externally thereof forimparting additional propelling effort to the ship as the impellerrotates; the diameter of the hub increasing rearwardly thereof to givethe hub a cone formation to remove air bubbles from the slip streamwithin the impeller.

11. Ship-propelling apparatus comprising a propeller shaft, a primarypropeller fixed to the shaft, a secondary shaft independent from theprimary shaft but located behind and coaxial therewith, a hub fixed tothe secondary shaft and disposed with one of its ends closely adjacentto the hub of the primary propeller, and a plurality of impeller bladesaround the hub extending radially therefrom and also in a directionlongitudinal thereof for the major part of their length but curved outof such substantially longitudinal direction at their ends remote fromthe propeller; and a cylindrical shell carried by the outer edges of theimpeller blades of a diameter at least as great as the primarypropeller, surrounding the hub coaxially therewith and extending alongthe hub for a distance greater than the width of the primary blades andfor the full length of the impeller blades, the forward end of the shellsurrounding a part of said primary propeller; in combination withsecondary propeller blades carried by the shell externally thereof;whereby the cylinder confines the slip stream from said primarypropeller, and the impeller blades receive the slip stream and both therotary and longitudinal components are translated into rotation of thesecondary blades in water outside the slip stream.

12. Ship-propelling apparatus comprising a propeller shaft, a primarypropeller fixed to the shaft, a strut carried by the hull of the shiprearwardly of the primary propeller, a separate shaft rotatably carriedby the strut behind the propeller shaft but coaxial therewith; a hubfixed to the separate shaft and disposed with one of its ends closelyadjacent to the hub of the primary propeller, and a plurality ofimpeller blades fixed to the hub and extending outwardly thereof, incombination with a cylindrical shell carried by the outer edges of theimpeller blades surrounding the hub coaxial therewith; the forward endof the shell surrounding a part of the primary propeller and the forwardedges of the impeller blades following the contour of the after edges ofthe blades of the primary propeller and being spaced therefrom with aminimum practical clearance; the hub being coned to expand rearwardlywithin the shell to remove air bubbles within the shell, and a pluralityof secondary propeller blades carried by the shell externally thereof;whereby the shell confines the slip stream from the primary propeller,the impeller blades receive the slip stream from the primary propellerto rotate the shell and the secondary propeller blades apply additionalpropelling force to the ship through said strut.

l3. Ship-propelling apparatus according to claim 1 in which vacuum ventsare provided around the circumference of the shell at a point just aftof the back edge of the primary propelling means.

14. Ship-propelling apparatus according to claim 1 in which theimpellers lie radially inside the shell, the forward part beingsubstantially in a direction longitudinal thereof but the rear end at anangle directed away from that direction in at least one fiat section.

15. Ship-propelling apparatus comprising a propeller shaft and a primarypropeller fixed to the propeller shaft, in combination with a shaftcarried by the ship independently of, coaxial with and rearwardly of itspropeller shaft, and separate impeller-propeller apparatus carried bythe independent shaft for rotation by the slip stream from the shipsprimary propeller; the impellerpropeller apparatus comprising a hubcarried by the independent shaft, the forward end of the hub having adiameter substantially equal to the diameter of the primary propellerhub and being disposed closely adjacent thereto to reduce turbulence andpartial vacuum in the slip stream, a plurality of impeller bladesextending outwardly from the hub and having their inner edges fixedthereto, a cylindrical shell coaxial with the hub fixed to the outeredges of the impeller blades surrounding the rearward part of the shipspropeller and extending rearwardly thereof the full length of theimpeller blades, the hub being coned in rearwardly expanding form withinthe shell to remove turbulence from the slip stream, and secondarypropeller means fixed externally to the cylinder, whereby theimpeller-propeller apparatus receives the slip stream from the shipsprimary propeller and is rotated thereby, and whereby rotation of saidimpeller-propeller apparatus provides additional propelling force to theship through the separate shaft.

16. Ship-propelling apparatus comprising a propeller shaft, a primarypropeller fixed to the shaft, a separate shaft suspended from the shipindependently of but coaxial with and rearwardly of its propeller shaft,and a separate impeller-propeller apparatus carried by the separateshaft for rotation by the slip stream from the ships primary propeller,the impeller-propeller apparatus comprising a hub carried by theseparate shaft, a plurality of impeller blades extending outwardly fromsaid hub and having their inner edges fixed thereto, a cylindrical shellcoaxial with the hub fixed to the outer edges of the impeller bladesclosely surrounding the rearward part of the ships propeller andextending rearwardly thereof to receive the slip stream from the shipsprimary propeller; the forward edges of the impeller blades followingthe contour of the after edges of the blades of the ships primarypropeller and being spaced therefrom with a minimum practical clearanceto insure maximum contact with the impeller blades by the slip stream,the forward edges of the impeller blades being fixed at an angle ofsubstantially 70 to to the direction of the slip stream, the impellerblades extending rearwardly of the impeller propeller apparatussubstantially parallel to the axis of the hub for substantially 75, oftheir length and then being curved away from the direction of the lengthof said impeller-propeller mechanism for substantially of their length,and a plurality of secondary propeller blades carried by the shellexternally thereof; whereby the slip stream from the ships primarypropeller rotates the impellerpropeller apparatus to provide additionalpropelling force to the ship through the separate shaft,

17. Ship-propelling apparatus having a propeller shaft, a primarypropeller fixed to the propeller shaft, a separate shaft suspended fromthe ship independently of but coaxial with and rearwardly of itspropeller shaft, and a separate impeller-propeller carried by theseparate shaft for rotation by the slip stream from the ships primarypropeller; the impeller-propeller apparatus comprising a hub carried bythe separate shaft, the forward end of the hub having a diametersubstantially equal to the diameter of the primary propeller hub andbeing disposed closely adjacent thereto to reduce turbulence and partialvacuum in the slip stream, a plurality of impeller blades extendingoutwardly from the hub and having their inner edges fixed thereto, acylindrical shell coaxial with the hub fixed to the outer edges of theimpeller blades closely surrounding the rearward part of the shipspropeller and extending rearwardly thereof to receive the slip streamfrom the ships primary propeller; the hub being coned in rearwardlyexpanding form within the shell to remove turbulence from the slipstream; the forward edges of said impeller blades following the contourof the after edges of the blades of the ships primary propeller andbeing spaced therefrom with a minimum practical clearance to insuremaximum contact with the impeller blades by the slip stream, the forwardedges of the impeller blades being fixed at an angle of substantially 70to 80 to the direction of the slip stream, the impeller blades extendingrearwardly of the primary propeller substantially parallel to the axisof the hub for substantially of their length and then being curved outof such substantially longitudinal direction for substantially of theirlength; and a plurality of secondary propeller blades carried by theshell externally thereof; whereby the slip stream from the ships primarypropeller rotates the impeller-propeller apparatus to provide additionalpropelling force to the ship through the separate shaft, substantiallyas described. 1

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 16,983 Leopold Apr. 7, 1857 2,127,747 Luther Aug. 23, 1938FOREIGN PATENTS Number Country Date 3,402 Great Britain Aug. 21, 188040,044 France Dec. 28, 1931 263,738 Germany Sept. 8, 1913 343,870 GreatBritain Feb. 26, 1931

